Corrugated fiberboard containers have been used for many years as shipping and storage containers for a large variety of products. Corrugated fiberboard generally refers to a multi-layer sheet material comprised of sheets of liner bonded to central corrugated layers of medium. Single-wall corrugated involves two sheets of liner bonded on alternate sides of one corrugated medium, while double-wall corrugated involves three liners bonded alternatively to two corrugated mediums. Corrugated fiberboard containers can vary greatly in size depending on the intended usage of the container.
The distribution of products in large containers is common in a wide variety of industries, from automotive to food. Corrugated semi-bulk containers (“CBCs”) serve as an example common in the meat industry for storing and shipping beef, pork, and other animal products between processing facilities, and from those processing facilities to customers. CBCs often require local horizontal zones of additional reinforcement for containment, to prevent container failure and ensure products are saleable when they arrive at the end of the distribution process and any auxiliary processes. Reinforcement methods are often used on CBCs and other corrugated containers in order to increase the performance more cost-effectively (by localizing the region of peak performance) than by switching to some other container material or increasing the overall strength of the corrugated component of the CBC.
Internal reinforcement of corrugated board can include polymeric straps located between one of the sheets of liner and one of the mediums to further enhance the bulge or tear resistance of the structure, increasing the performance of the overall container. However, even when polymeric straps are included within the corrugated board structure, a weak spot will occur at the manufacturing joint, which is the area of overlap of the fiberboard sheet when a container is formed. Because the corrugated board is discontinuous at this joint, the internal reinforcement is also discontinuous, creating a failure nucleation zone at the joint. This weakness is typically overcome by using external reinforcement in conjunction with or in lieu of internal reinforcement.
External reinforcement is most often accomplished by the use of multiple horizontal bands of strapping material. These external reinforcing straps may be placed on the container when it is in a flat semi-assembled orientation before being formed into a typically shaped container (“knocked down”) or may be applied after the container has been formed into its final typical shape (“set-up”). Previous reinforcing straps have been made from metallic materials or polymeric materials. The reinforcing straps are formed onto a set-up CBC or around a knocked down CBC in a continuous loop, with the two ends of the strapping material typically attached together using methods common in the industry. Metallic straps may be crimped together, while polymeric straps may be heat welded together.
Frequently, reinforcing straps are applied so that the spacing between two adjacent straps is generally equal around the periphery of the container, whether they are applied to containers in a knocked down or set up configuration, i.e. the straps are typically parallel. The reinforcing straps are spaced some distance apart along the height of the container. When straps are applied to a container in a set up configuration, the reinforcing straps are typically applied one-at-a-time by one or more individuals. The process of adding reinforcing straps to the container in a set up configuration often results in large variations in strap placement and strap tightness when comparing several containers, with an associated variation in strap impact on overall container performance.
Reinforcing straps applied to containers while the containers are in a knocked down orientation typically are applied in a semi-automated process. In the semi-automated mode one automatic strapper is used to apply straps. One or more individuals moves the knocked down CBC through the strapper manually, with the external straps applied at predetermined locations. While this process only requires one strapping machine, it is quite slow and requires significant manual labor. Strap placement accuracy depends on the patience and attention of the operators. This process can be automated (intermittent motion) on a conveyor, by having the CBC stop at fixed locations relative to the individual strapper, so that the external straps are applied at the specified locations. It can be further automated by using one strapping machine for every band/strap placed on the box (frequently 3 or more). Not only does this require extensive capital expense but also a dedicated manufacturing line. Initial strap placement is typically controlled to within roughly one-to-two strap widths of the target location, depending on the mechanism by which the knocked down CBC is started and stopped on the manufacturing line.
Reinforcing straps currently used are individually joined continuous loops that are not physically attached to the container so as to prevent movement or sliding of the bands. They rely on the tension of the strapping material as well as friction to stay in place. If the tension is high, the strap will remain precisely where placed at the risk of also deforming or damaging the CBC, potentially decreasing container performance. Typically, tension levels are set to avoid significantly damaging the container while allowing the strap to remain in an intended location by friction. When strap tension level is low, bands often slip from their intended locations when the containers are put into use, increasing the likelihood of lower container performance.
Additionally, reinforcement straps currently used typically have a much higher elongation at failure compared to the corrugated fiberboard material used to make the containers. Corrugated fiberboard typically has an elongation at failure of about between one and a half percent and two percent (1.5%-2%). Many polymeric reinforcement straps used currently have an elongation at failure of about fifteen percent (15%). This near order of magnitude difference of elongation at failure requires that the strapping material used be selected so that it has the necessary strength to reinforce the container at the elongation of failure of the corrugated fiberboard, to ensure that the straps help prevent the failure of the fiberboard, not simply help to contain the contents of the container after the fiberboard fails. This is important as some customers will not accept the contents of a container if the container has been breached. Using a material in a reinforcing strap that has the required strength at the elongation at failure of the corrugated material typically requires that a much stronger material be used, as most materials have their greatest strength just prior to failure. Thus, the majority of the strength of the reinforcing strap goes unused.
Thus, it would be desirable to use a reinforcement material that is physically attached to the container, and which further is made of one continuous piece to allow for quicker application. It would be further desirable to use a reinforcing material with a more similar elongation at failure than that typically used currently for container reinforcement.